The present disclosure relates to a developing device in which developer is conveyed and an image forming apparatus provided with the same.
Conventionally, a developing device is known in which developer is conveyed in a circulating manner between a first conveyance path and a second conveyance path arranged in a developer housing. The developer is conveyed in opposite directions in the first and second conveyance paths by agitating screws arranged in the respective first and second conveyance paths. The agitating screw of the developing device is composed of a shaft portion and a spiral piece arranged around the shaft portion. In the developer housing, the developer is conveyed in a predetermined conveying direction by driving and rotating the agitating screws.
If an adhesion force of the developer increases as the developer is deteriorated, the developer may adhere to the shaft portion. If the developer adheres to the shaft portion, virtual shaft thickening of the agitating screw occurs to reduce the conveying performance of the agitating screw. An agitating screw including no shaft part, i.e. having a hollow shape in an axial central part thereof to solve the shaft thickening of the agitating screw described above is known.
With the agitating screw described above, developer conveying performance in an axial direction tends to be lower as compared with an agitating screw including a shaft portion extending in the axial direction. Thus, the conveying performance in the axial direction of the agitating screw has been affected by surrounding members in some cases. Particularly, with the agitating screw arranged adjacent to a developing roller for carrying developer with a magnetic force, the conveying performance of the agitating screw is subject to fluctuation depending on the developing roller. As a result, there has been a difference in the conveying performance between the agitating screw arranged in the first conveyance path adjacent to the developing roller and that arranged in the second conveyance path distant from the developing roller in some cases. This has resulted in a problem that the circulation of the developer in the developer housing becomes unstable.
The present disclosure was developed in view of the above problem and an object thereof is to adjust a conveying ability of a developer conveying member having a hollow shape by a simple configuration.